Latching relays are used widely in applications such as aerospace, RF communications and portable electronics. Conventional electromechanical relays operate by energizing an electromagnet that actuates a magnetic armature to make or break a contact. When the magnet is deenergized, a spring restores the armature to its original position. Similar techniques have been applied to microelectromechanical (MEMS) relays using microelectronic fabrication methods. Latching in MEMS switches is difficult to achieve. One approach uses a cantilever beam in the magnetic field of a permanent magnet. The beam is bistable; the end closer to the magnet is attracted to the magnet.
Liquid metal is also used in electrical relays. A liquid metal droplet can be moved by a variety of techniques, including electrostatic forces, variable geometry due to thermal expansion/contraction, and pressure gradients. When the dimension of interest shrinks, the surface tension of the liquid metal becomes dominant force over other forces, such as body forces (inertia). Consequently, some microelectromechanical (MEM) systems utilize liquid metal switching.